1. Field of the Invention
The present invention relates to a heat storage device that temporarily accumulates heat (or cold energy) held in a medium such as a refrigerant or the like.
2. Description of the Related Art
In the art related to the invention, a compression type heat pump is known as one example of a heating device. The fundamental construction thereof is that a compressor compresses a refrigerant gas, the refrigerant gas dissipates heat so that it condenses, and then, the refrigerant is expanded adiabatically, and absorbs external heat so that it vaporizes, and thereafter is compressed again. Accordingly, if for example a vehicle is to be air conditioned, the air within the passenger compartment is cooled by taking advantage of the action of the refrigerant to absorb heat, so that the air in the passenger compartment is cooled.
In a vehicle, the power source for propelling the vehicle, such as an engine or the like, is used to drive the heat pump. Accordingly, if the vehicle is stationary, the power source drives the compressor by raising the idling rotational speed of the engine. Conversely, if the vehicle runs at a comparatively high speed while coasting, it is possible that the compressor may be driven to an excessive degree. Moreover, the heat that is created along with the air conditioning, in other words the heat held in the refrigerant, which is compressed, is transferred to the outside environment. Since, with the power being primarily outputted by the power source for driving the vehicle in this manner, from the point of view of the heat pump, the power supply is unstable, accordingly the loss of energy becomes great, and, by extension, there is a possibility that the fuel consumption of the vehicle will increase.
In the past, Japanese Patent Application Publication No. 5-286350 (JP H5-286350) describes an air conditioning device in which thermal accumulators are fitted both to a condenser in which pressurized refrigerant is condensed and to an evaporator in which the refrigerant is adiabatically expanded and vaporized, in order to utilize energy more effectively. With this air conditioning device, on the one hand, the heat that is emitted from the condenser is accumulated in the heat storage material, and it is arranged to use the heat in the heat storage material for heating, by selectively circulating brine (a thermal medium) between this heat storage material and a heat dissipation section of a heat exchanger within the passenger compartment, or a panel heater or the like for room heating. Furthermore, the temperature of the cold storage material is decreased by the evaporator absorbing heat from the cold storage material, and it is arranged to perform air conditioning by the cold storage material, by selectively circulating another brine (a thermal medium) between this cold storage material and a heat exchange device within the passenger compartment.
Furthermore, in Japanese Patent Application Publication No. 7-4686 (JP H7-4686), there is described an air conditioning device which is provided with a heat exchanger for cold storage and a heat exchanger for heat storage, and this is suitable as a so called stationary air conditioning device, such as one for household use or the like. Moreover, Japanese Patent Application Publication No. 2003-336974 (JP 2003-336974), describes a heat storage type heat exchanger; and, along with a heat source fluid and a heat recovery fluid being brought into mutual contact via a wall surface, the heat exchanger incorporates a heat storage material around flow conduits in which these respective fluids flow.
A technique for converting heat into electric power by using a thermoelectric element and storing the electricity is described in Japanese Patent Application Publication No. 6-22572 (JP H6-22572). Furthermore, in Japanese Patent Application Publication No. 1-247932 (JP H1-247932), there is described a technique in which, when heat exchange is not necessary, in order to prevent useless heat dissipation or heat absorption via the thermal medium, the thermal medium is drained from a heat exchanger on the side interior to the vehicle.
As described in JP H5-286350, JP H7-4686, and JP 2003-336974, if a heat storage material, which is able store heat or cold is employed, then heat is not radiated uselessly, and, since it is possible to perform heat recovery or energy recovery, accordingly it becomes possible to enhance the fuel consumption of the vehicle. However, because the refrigerant, which is circulating in the refrigerant cycle, and the brine (the thermal medium), which is circulating to the heat exchanger within the passenger compartment, for air conditioning are both circulated according to demand, accordingly the time period of heat exchange in the heat storage type heat exchanger between the refrigerant and the brine (the thermal medium) or the heat storage material, and the heat exchange area and the like, impose a limitation, and there is a possibility that it may not necessarily be possible to perform heat storage or cold storage sufficiently. Furthermore, since there is also a limitation upon the amount of heat that can be stored in the heat storage material, accordingly there is a possibility that it will not be possible sufficiently to recover the heat that could be recovered. In this case, the heat in the refrigerant is not sufficiently dissipated by the thermal accumulator so that it does not go into the supercooled state, and the amount of heat transported by the refrigerant becomes relatively small, or the refrigerant gas is supplied to the cold storage device just as it is, so that, along therewith, there is a possibility that the thermal efficiency of the refrigeration cycle will be reduced.